702 
Hill and de Frame . — On the 
already indicated; the bundle marked a formed one pole of the root, 
b and c formed the second, while the two remaining bundles, d and 
formed the third. 
The strands b and c, and d and *, acted in the same fashion as the 
bundles a and b in the seedling with four cotyledons (Diag. 4). It 
may therefore be concluded, from the behaviour of the vascular bundles, 
that of the five seed-leaves one (a) represents a whole cotyledon, while 
the rest are half-cotyledons, although a second complication has been 
introduced by the fusion of several of the seed-leaves. 
Cnpressus macrocarp a, Hartweg. The number of seed-leaves is three 
or four ; their structure is the same as in the foregoing species, but they 
are very much narrower, their shape in transverse section being similar to 
that of the half-cotyledons of C. torulosa (Diag. 4, Fig. 1). 
Transition. The seed-leaf traces, in a plant with three cotyledons 
(Series A), behave like bundles c and d of C . torulosa (Diag. 4) ; that 
is to say, the phloem of each strand bifurcates during the inward passage 
and the protoxylem begins to take up the exarch position. These move- 
ments are soon completed at a lower level in the hypocotyl, and thus 
a triarch root results. 
In one seedling examined, having four cotyledons (Series B), the 
transition took place on exactly the same lines as that described for that 
plant of C. torulosa (Series C) which also had four seed-leaves (Diag. 4), 
the only difference being that in C. macrocarpa each of the four cotyledons 
was quite freely inserted on the axis. Thus of the four seed-leaves, two 
are equivalent to half-cotyledons, the remaining two being whole cotyledons. 
It may here be stated that the evidence for the splitting of the seed-leaves 
is much more abundant in the normally polycotyledonous plants of the 
Abietineae, and will be dealt with fully later on. 
Libocedrus decurrens , Torr. Two seedlings only were available for 
the purposes of this investigation, and of these one alone was suitable 
for the study of the transition-phenomena, owing to the presence of 
extensive secondary thickening in the other. The older of these had 
two cotyledons, while the younger, which is considered below, had three 
(Fig. 5, Plate XXXV) ; Professor Lawson informs us, however, that the usual 
number of seed-leaves is two. 
Although the structure and transition is of the same type as has 
been described above, the transition from stem to root-structure is very 
much slower than in any of the preceding plants. The upper part of 
the hypocotyledonary axis exhibits stem -structure, and the rearrangement 
of the vascular tissues is very gradual. The phloem of any one bundle 
diverges on each side of the wood and fuses with the corresponding masses 
of bast derived from the adjacent bundles ; hence a radial arrangement of 
the essential tissues results. The redistribution of the elements of the 
